1. Field of the Invention
The invention relates to a method of precoding, and more particularly, to a method of joint clustering and precoding and a base station using the same.
2. Description of Related Art
In the fourth generation mobile communication system, the orthogonal multiple access (OMA) system is widely used for accomplishing favorable system capacity. Yet, with advancements in technologies, the demand for system capacity will be increasingly higher for the future wireless communication. Therefore, the non-orthogonal multiple access (NOMA) system gradually becomes more important each day for the next (e.g., fifth) generation mobile communication system.
The NOMA system is capable of superposing the messages to multiple users with the appropriate power allocation between the users for allowing the users to access the same channel resources (e.g., the same time and frequency) and simultaneously transmitting the messages; and separates the superposed message for the users at the receiver by using the successive interference cancellation (SIC) technology. In general, the NOMA technology is capable of improving a use efficiency of the system resources to achieve a system capacity higher than that of the OMA technology.
Nonetheless, improvements are still to be constantly made to the design for the NOMA system. For example, it is a very important issue that must be addressed as how to deal with the interference between multiple users in order to accomplish the goal for maximizing the system capacity. In other words, the optimization of the overall transmission performance for the NOMA system is one of the subject matters concerned by person skilled in the art.